As one of the route control procedures of a network communication, a route control procedure which uses the OpenFlow technique being a control protocol of communication devices has been studied. The non-patent literatures 1 and 2 describe the OpenFlow technique in detail. A network whose route control is performed by the OpenFlow network is called as the OpenFlow network.
In the OpenFlow network, the behavior of a switch is controlled by a controller like the OFC (OpenFlow Controller) operating the Flow Table of a switch like the OFS (OpenFlow Switch). A link between the controller and the switch is connected by the Secure Channel for controlling the switch by the controller using a control message complying with the OpenFlow protocol.
The switch of the OpenFlow network indicates an edge switch and a core switch which form an OpenFlow network and subjected to the control of a controller. In the OpenFlow network, the sequence of flows of a packet from the reception of the packet (a communication data) at an input side edge switch to the sending of the packet at the output side edge switch is called as the Flow.
The Flow Table is a table in which a Flow entry, which defines a predetermined processing (action) to be performed to a packet group (packet series) being matched with a predetermined match condition (rule), is registered.
The rule of the Flow entry is defined by various combinations of any or all of the Destination Address, the Source Address, the Destination Port, the Source port, which are included in the header region of each protocol level of the packet, and can be distinguished to each other. In addition, the information of the Ingress Port can also be used as a rule of the Flow entry.
The action of the flow entry indicates an operation such as “outputting to a specific port”, “discard”, “rewriting of the header” and the like. For example, if identification information (output port number and the like) is indicated in the action of the flow entry, the switch outputs the packet to the corresponding port. If the identification information of the output port is not indicated, the packet is discarded. Or, if header information is indicated in the action of the flow entry, the switch rewrites the header of the packet based on the indicated header information.
Each switch of the OpenFlow network performs the action of the flow entry to the packet group being matched with the rule of the flow entry registered in the flow table.
However, there is a limit in the amount of the memory for the flow table mounted on a switch, so that the number of flow entries which can be registered in a switch has an upper limit. Therefore, there is a problem that, when the number of the registered flow entries reaches the upper limit, it becomes impossible to register a new flow entry, and a communication data is not forwarded by the procedure based on the control from the control server.
There is also a problem that, when the type of the flow entry is defined in detail, the number of the flow entries to be registered increases, so that the amount of the memory for the flow table may become insufficient. As a result, in addition to the upper limit of the number of the flow entry, there has been a problem that the types of the Flow available to the system design have an upper limit.